Method of segmenting semiconductor wafer

ABSTRACT

To provide a method of segmenting a semiconductor wafer, which is capable of preventing chippings. 
     A semiconductor wafer  1  is partitioned into a circumferential ring-shaped region  1   a  and a segmentation region placed in the inner side of the ring-shaped region  1   a . The semiconductor wafer  1  included in the segmentation region is cut into the form of a lattice along a plurality of perpendicular cutting lines  4  and is segmented into a plurality of chips  2 . On the other hand, the semiconductor wafer  1  included in the ring-shaped region  1   a  is cut along two partition lines  5  extending in parallel to the cutting lines  4  from the center O of the semiconductor wafer  1  and is partitioned into four independent regions.

TECHNICAL FIELD

The present invention relates to a method of segmenting a semiconductorwafer into a plurality of chips by means of plasma etching.

BACKGROUND ART

As a semiconductor wafer has been thinner and thinner, instead of amethod of segmenting a semiconductor wafer into a plurality of chipsusing a cutting tool such as a blade or the like, where there may occurdefects or cracks in the semiconductor wafer, which may lead to lowyield, a plasma etching method has recently attracted a great attention.In this plasma etching method, a semiconductor wafer whose circuitforming side is attached with a protective sheet is hermetically sealedin a plasma treating chamber and is segmented into a plurality of chipsby subjecting the semiconductor wafer to plasma etching from other sideof the semiconductor wafer, the protective sheet serving to prevent thechips from being dispersed and protect circuits (see Patent Document 1).

-   [Patent Document 1] Japanese Unexamined Patent Application    Publication No. 2005-191039

DISCLOSURE OF THE INVENTION Technical Problem

After the semiconductor wafer is subjected to the plasma etching to besegmented into the plurality of chips, the semiconductor wafer can notkeep a flat state, and there occur chippings (defects or cracks) due tocontact between adjacent chips by bend or deflection of the protectivesheet, which may result in low yield. It is expected that this problembecomes more serious as a gap between adjacent chips becomes smaller andsmaller due to narrower etching width.

It is therefore an object of the invention to provide a method ofsegmenting a semiconductor wafer into a plurality of chips, which iscapable of preventing chippings of the chips.

Technical Solution

According to an aspect of the invention, there is provided a method ofsegmenting a semiconductor wafer into a plurality of chips by means ofplasma etching, a protective sheet being provided on a circuit formingsurface of the semiconductor wafer, including the steps of segmenting asegmentation region, which is partitioned in an inner side of aring-shaped region partitioned in the circumference of the semiconductorwafer, into the plurality of chips by cutting the segmentation regionalong a plurality of perpendicular cutting lines; and partitioning thering-shaped region into four independent regions by cutting thering-shaped region along two partition lines extending in parallel tothe perpendicular cutting lines from the center of the semiconductorwafer.

Preferably, the method further includes the step of masking a regionwhich is in a rear side of the semiconductor wafer and lies in theoutside of the regions corresponding to the cutting lines and thepartition line. The masked semiconductor wafer is subjected to plasmaetching treatment to segment the segmentation region into the pluralityof chips and partition the ring-shaped region into the four independentregions.

Preferably, the method further includes the steps of: attaching acontinuous extensible maintenance sheet to the rear side of thesemiconductor wafer in which the segmentation region is segmented intothe plurality of chips and the ring-shaped region is partitioned intothe four independent regions; peeling the protective sheet; andexpanding a gap between adjacent chips and a gap between the chips andthe ring-shaped region by extending the maintenance sheet from an innerside to an outer side of the semiconductor wafer.

According to another aspect of the invention, there is provided a methodof segmenting a semiconductor wafer into a plurality of chips by meansof plasma etching, a protective sheet being provided in a circuitforming surface of the semiconductor wafer, including the steps of:segmenting a segmentation region, which is partitioned in an inner sideof a ring-shaped region partitioned in the circumference of thesemiconductor wafer, into the plurality of chips by cutting thesegmentation region along a plurality of perpendicular cutting lines;and partitioning the ring-shaped region into more than five independentregions by cutting the ring-shaped region along partition lines. Thepartition lines include at least two partition lines extending inparallel to the perpendicular cutting lines from the center of thesemiconductor wafer, and a region whose circumferential length is morethan ⅛ of the entire circumferential length of the semiconductor waferis necessarily included in each of the regions partitioned along the twopartition lines.

Preferably, the method further includes the step of masking a regionwhich is in a rear side of the semiconductor wafer and lies in theoutside of the regions corresponding to the cutting lines and thepartition line. The masked semiconductor wafer is subjected to plasmaetching treatment to segment the segmentation region into the pluralityof chips and partition the ring-shaped region into more than fiveindependent regions.

Preferably, the method further includes the steps of: attaching acontinuous extensible maintenance sheet to the rear side of thesemiconductor wafer in which the segmentation region is segmented intothe plurality of chips and the ring-shaped region is partitioned intomore than five independent regions; peeling the protective sheet; andexpanding a gap between adjacent chips and a gap between the chips andthe ring-shaped region by extending the maintenance sheet from an innerside to an outer side of the semiconductor wafer.

Advantageous Effects

According to the present invention, since bend of the maintenance sheetis suppressed as at least an edge of the semiconductor wafer is notsegmented, generation of chippings due to contact between segmentedchips is reduced, which results in increase of a yield.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a plan view of a segmented semiconductor wafer according to anembodiment of the present invention.

FIG. 2 is a sectional view taken along line A-A in FIG. 1.

FIG. 3 shows side sectional views for illustrating steps of a method ofsegmenting a semiconductor wafer by means of plasma etching according toan embodiment of the present invention.

FIG. 4 is a side sectional view showing a state where a semiconductorwafer is carried in a plasma treating chamber, according to anembodiment of the present invention.

FIG. 5 is a side sectional view showing a state where a semiconductorwafer is carried out of a plasma treating chamber, according to anembodiment of the present invention.

FIG. 6 is a side sectional view showing a state where a semiconductorwafer is absorbed to a robot hand, according to an embodiment of thepresent invention.

FIG. 7 shows side sectional views showing a state where a semiconductorwafer is mounted on a pickup stage, according to an embodiment of thepresent invention.

FIG. 8 is a plan view showing a state where a semiconductor wafer ismounted on a pickup stage, according to an embodiment of the presentinvention.

FIG. 9 is a plan view of a segmented semiconductor wafer according toanother embodiment of the present invention.

FIG. 10 is a plan view of a segmented semiconductor wafer according tostill another embodiment of the present invention.

BEST MODE FOR CARRYING OUT THE INVENTION

Embodiments of the present invention will be hereinafter described withreference to the drawings. FIG. 1 is a plan view of a segmentedsemiconductor wafer according to an embodiment of the present inventionand FIG. 2 is a sectional view taken along line A-A in FIG. 1. Asemiconductor wafer 1 is a disk-like plate formed by slicing an ingot,which is made by crystal-growing silicon, germanium, gallium-arsenic orthe like into a cylindrical shape, at thickness of 0.5 mm to 1.5 mm. Adiameter of the semiconductor wafer 1 is generally 5 inches (125 mm), 8inches (200 mm) or 12 inches (300 mm). A circuit pattern (integratedcircuit) is formed on one surface (circuit forming surface) of thesemiconductor wafer 1 and is segmented into a plurality of parts, i.e.,chips (IC chips) 2 by means of plasma etching. A protective sheet 3 isattached to the circuit forming surface and serves to prevent the chips2 from being dispersed and prevent the circuit forming surface frombeing damaged when the circuit pattern is segmented.

The semiconductor wafer 1 is partitioned into a circumferentialring-shaped region 1 a and a segmentation region 1 b placed in the innerside of the ring-shaped region 1 a. The semiconductor wafer 1 includedin the segmentation region 1 b is cut into the form of a lattice along aplurality of perpendicular cutting lines 4 and is segmented into aplurality of chips 2. On the other hand, the semiconductor wafer 1included in the ring-shaped region 1 a is cut along two partition lines5 extending in parallel to the cutting lines 4 from the center O of thesemiconductor wafer 1 and is partitioned into four independent regions.

FIG. 3 shows side sectional views for illustrating steps of a method ofsegmenting the semiconductor wafer. First, (a) the protective sheet 3 isattached to the circuit forming surface of the semiconductor wafer 1,and (b) the semiconductor wafer 1 is polished until it has apredetermined thickness. Next, (c) regions, which are in a rear side ofthe circuit forming surface of the semiconductor wafer 1 and lie in theoutside of the cutting lines 4 and the partition lines 5, are maskedwith an etching-resistant resist 6. The resist 6 is for masking aportion that will not be etched in a later plasma treating process. Theresist 6 masks the entire rear surface of the semiconductor wafer 1 andthen portions of the resist 6, which correspond to the cutting lines 4and the partition lines 5, are removed. Next, (d) the semiconductorwafer 1 is subjected to plasma treatment, the semiconductor wafer 1 iscut along the cutting lines 4 and the partition lines 5, thesegmentation region 1 b is segmented into the plurality of chips 2, andthe ring-shaped region 1 a is partitioned into the four independentregions, and (e) the remaining resist 6 is ashed by ozone or plasma invapor to be completely removed from the semiconductor wafer 1.

FIG. 4 is a side sectional view showing a state where a semiconductorwafer is carried in a chamber for plasma treatment. A chamber 7 forms asealed space therein, an electrode 9 connected to a high frequency powersupply 8 is arranged in a lower side of the chamber 7, and a groundedelectrode 10 opposing the electrode 9. The lower electrode 9 also servesas a support of the semiconductor wafer 1. The semiconductor wafer 1 issupported on the electrode 9 with the protective sheet 3 directingdownward. When a high frequency voltage is applied to the electrode 9 ina state where the chamber 7 is decompressed below a predeterminedpressure and is filled with gas for plasma generation, the semiconductorwafer 1 is cut by plasma etching along the cutting lines 4 and thepartitions 5, both of which are not masked with the resist 6.

FIG. 5 is a side sectional view showing a state where the semiconductorwafer is carried out of the chamber for plasma treatment. After thechamber 7 is opened to the air, a door 7 a of a side wall of the chamber7 is opened to form an opening 7 b and a robot hand 11 is advanced intothe chamber 7 through the opening 7 b to vacuum-hold the semiconductorwafer 1 from its upper side and carry it out of the chamber 7 with itheld to the robot hand 11.

FIG. 6 is a side sectional view showing a state where the semiconductorwafer is vacuum-held to the robot hand. Although the circumferentialring-shaped region 1 a of the plasma-etched semiconductor wafer ispartitioned into the four independent regions, since each independentregion has an area sufficiently larger than the individual chips 2, ithas a function of preventing the protective sheet 3 located in an innerside from being bent by its rigidity. On this account, even if thereoccurs an unbalance of a suction force due to shock, vibration or changeof a negative pressure when the robot hand 11 vacuum-holds and carriesthe semiconductor wafer 1, the bend of the protective sheet 3 isminimized, thereby preventing adjacent chips 2 from contacting with eachother, which results in reduction of a risk to generate chippings(defects and cracks).

In the semiconductor wafer 1 carried out of the chamber 7 by the robothand 11, an extensible maintenance sheet 12 is attached to a rear sideof the circuit forming surface and then the protective sheet 3 is peeledout to expose the circuit forming surface, as shown in a part (f) inFIG. 3. A shape maintenance ring 13 having high rigidity is provided ina portion surrounding the plurality of chips 2 of the maintenance sheet12 in order to maintain flatness and tension of the maintenance sheet12.

FIG. 7 shows side sectional views showing a state where thesemiconductor wafer 1 is mounted on a pickup stage. (a) The maintenancesheet 12 is placed on a cylindrical expand member 14 provided in thepickup stage with the semiconductor wafer 1 directing upward, (b) theshape maintenance ring 13 is pressed down at an outer side of the expandmember 14 and the maintenance sheet 12 is extended in a direction (arrowa) from the inner side to the outer side of the semiconductor wafer 1.As shown in FIG. 8, since the ring-shaped region 1 a surrounding theplurality of chips 2 is partitioned into the four independent regionsalong the perpendicular partition lines, when the maintenance sheet 12is extended from the inner side to the outer side of the semiconductorwafer 1, the four independent regions of the ring-shaped region 1 a aremoved (arrow b) in such a manner that they are alienated from eachother, the maintenance sheet 12 located at the inner side of thering-shaped region 1 a is extended from the inner side to the outer sideof the semiconductor wafer 1, and a gap between adjacent chips 2 and agap between the chips 2 and the ring-shaped region 1 a are widened. (c)With the gap between adjacent chips 2 widened for pickup of the chips,the chips 2 are absorbed by a nozzle 15 from the circuit formingsurface, and at the same time, the chips 2 are pushed up by an ejector16 from a rear side of the maintenance sheet 12 to pick up the chips 2from the maintenance sheet 12.

In the above-described semiconductor wafer 1, although thecircumferential ring-shaped region 1 a is partitioned into the fouruniform independent regions along the two partition lines 5 extending inthe direction in parallel to the cutting lines 4 from the center O ofthe semiconductor wafer 1, the ring-shaped region 1 a may be partitionedinto more than five independent regions. In this case, it is a requiredcondition that a region whose circumferential length is more than ⅛ ofthe entire circumferential length of the semiconductor wafer 1 isnecessarily included in each of the four independent regions. Since theregion having such a circumferential length has an area sufficientlylarger than the individual chips 2, bend of the protective sheet 3 canbe effectively suppressed when such a region is arranged in balance inthe circumference of the semiconductor wafer 1.

FIGS. 9 and 10 are plan views of a segmented semiconductor waferaccording to another embodiment of the present invention. In asemiconductor wafer 17 shown in FIG. 9, a circumferential ring-shapedregion 17 a is partitioned into eight independent regions by cutting thering-shaped region 17 a along two partition lines 18 extending inparallel to cutting lines 4 from the center O of the semiconductor wafer17 and two partition lines 19 extending in a direction making an angleof 45 degrees with the two partition lines 18. The eight independentregions are equally divided such that their circumferential lengthcorresponds to ⅛ of the entire circumferential length of thesemiconductor wafer. Although the eight independent regions each have anarea corresponding to ½ of an area of each of the four independentregions, since the eight independent regions have the area sufficientlylarger than the individual chips 2 and are arranged in balance everycenter angle of 45 degrees of the semiconductor wafer 17, they cansufficiently exhibit a function of preventing the protective sheetlocated at the inner side from being bent. In addition, by partitioningthe ring-shaped region 17 a into the eight independent regions, since adegree of freedom of an extension direction of the maintenance sheetlocated in the inner side of the ring-shaped region 17 a is increased,it is possible to expand the chips 2 with more suitable intervals.

In a semiconductor wafer 20 shown in FIG. 10, a circumferentialring-shaped region is partitioned into 12 independent regions by cuttingthe ring-shaped region along two partition lines 21 extending inparallel to cutting lines 4 from the center O of the semiconductor wafer20 and four partition lines 22 similarly extending from the center O.While regions 20 a of the 12 independent regions, which are partitionedalong the partition lines 21 and the partition lines 22, have a smallarea, regions 20 b partitioned along the partition lines 22 and thepartition lines 22 have a circumferential length which is more than ⅛ ofthe entire circumferential length of the semiconductor wafer and have anarea sufficiently larger than the individual chips 2. In addition, sincethe regions 20 b are arranged in balance every center angle of 90degrees of the semiconductor wafer 20, they can sufficiently exhibit afunction of preventing the protective sheet located at the inner sidefrom being bent.

INDUSTRIAL APPLICABILITY

According to the present invention, since the bend of the maintenancesheet is suppressed as at least an edge of the semiconductor wafer isnot segmented, generation of chippings due to contact between segmentedchips is reduced, which results in increase of a yield, and thus thepresent invention is useful in a field of semiconductor chip mounting.

1. A method of segmenting a semiconductor wafer into a plurality ofchips by means of plasma etching, the semiconductor wafer beingpartitioned into a ring-shaped non-segmentation region including theperimeter of the semiconductor wafer and a segmentation region placed inan inner side of the ring-shaped non-segmentation region, a protectivesheet being provided in a circuit forming surface of the semiconductorwafer, comprising the steps of: segmenting the segmentation region intothe plurality of chips by cutting the segmentation region along aplurality of perpendicular cutting lines; and partitioning thering-shaped non-segmentation region into four independent non-segmentedregions by cutting the ring-shaped non-segmentation region along twopartition lines extending in parallel to the perpendicular cutting linesfrom the center of the semiconductor wafer.
 2. The method according toclaim 1, further comprising the step of masking a region which is in arear side of the semiconductor wafer and lies in the outside of theregions corresponding to the cutting lines and the partition line,wherein the masked semiconductor wafer is subjected to plasma etchingtreatment to segment the segmentation region into the plurality of chipsand partition the ring-shaped non-segmentation region into the fourindependent non-segmented regions.
 3. The method according to claim 2,further comprising the steps of: attaching a continuous extensiblemaintenance sheet to the rear side of the semiconductor wafer in whichthe segmentation region is segmented into the plurality of chips and thering-shaped non-segmentation region is partitioned into the fourindependent non-segmented regions; peeling the protective sheet; andexpanding a gap between adjacent chips and a gap between the chips andthe ring-shaped non-segmentation region by extending the maintenancesheet from an inner side to an outer side of the semiconductor wafer. 4.A method of segmenting a semiconductor wafer into a plurality of chipsby means of plasma etching, the semiconductor wafer being partitionedinto a ring-shaped non-segmentation region including the perimeter ofthe semiconductor wafer and a segmentation region placed in an innerside of the ring-shaped non-segmentation region, a protective sheetbeing provided in a circuit forming surface of the semiconductor wafer,comprising the steps of: segmenting the segmentation region into theplurality of chips by cutting the segmentation region along a pluralityof perpendicular cutting lines; and partitioning the ring-shapednon-segmentation region into more than five independent non-segmentedregions by cutting the ring-shaped non-segmentation region alongpartition lines, wherein the partition lines include at least twopartition lines extending in parallel to the perpendicular cutting linesfrom the center of the semiconductor wafer, and a region whose perimeterlength is more than ⅛ of the entire perimeter length of thesemiconductor wafer is necessarily included in each of the regionspartitioned along the two partition lines.
 5. The method according toclaim 4, further comprising the step of masking a region which is in arear side of the semiconductor wafer and lies in the outside of theregions corresponding to the cutting lines and the partition line,wherein the masked semiconductor wafer is subjected to plasma etchingtreatment to segment the segmentation region into the plurality of chipsand partition the ring-shaped non-segmentation region into more thanfive independent non-segmented regions.
 6. The method according to claim5, further comprising the steps of: attaching a continuous extensiblemaintenance sheet to the rear side of the semiconductor wafer in whichthe segmentation region is segmented into the plurality of chips and thering-shaped non-segmentation region is partitioned into more than fiveindependent non-segmented regions; peeling the protective sheet; andexpanding a gap between adjacent chips and a gap between the chips andthe ring-shaped non-segmentation region by extending the maintenancesheet from an inner side to an outer side of the semiconductor wafer. 7.The method according to claim 1, wherein the perpendicular cutting linesdo not reach the perimeter of the semiconductor wafer, and the twopartition lines reach the perimeter of the semiconductor wafer.
 8. Themethod according to claim 4, wherein the perpendicular cutting lines donot reach the perimeter of the semiconductor wafer, and the twopartition lines reach the perimeter of the semiconductor wafer.
 9. Themethod according to claim 1, wherein each of independent non-segmentedregions has an area larger than each of the plurality of chips.
 10. Themethod according to claim 4, wherein each of independent non-segmentedregions has an area larger than each of the plurality of chips.